Grinding machine control



19, 1967 M. RUDERFER ETAL 3,358,405

GRINDING MACHINE CONTROL Filed Dec. 18, 1964 2 Sheets-Sheet 1 FIG. 1

INVENTORS Philip Ohringer Martin Ruderfer ATTORNEYS J Dec. 19, 1967 M. RUDERFER ETAL 3,358,405

GRINDING MACHINE CONTROL 2 Sheets-Sheet 2 Filed Dec. 18, 1964 3 )bbbbk T .3 m N M u SR 5 T;

United States Patent 3,358,405 GRINDING MACHINE CONTROL Martin Ruderfer, Hempstead, and Philip Ohringer, Commack, N.Y. (both of 95 Madison Ave., Hempstead, NY. 11550) Filed Dec. 18, 1964, Ser. No. 419,534 2 Claims. (Cl. 51-103) ABSTRACT OF THE DISCLOSURE The disclosure shows a method and apparatus for controlling a centerless throughfeed grinding machine and for correcting grinding wheel breakdown in such a machine. The'apparatus provides for retracting the regulating wheel of the grinder away from a series of moving workpieces, and a first grinding position, halting the movement of the workpieces, automatically advancing the regulating wheel back toward the workpieces, restarting the movement of the workpieces, and halting the regulating wheel at a second grinding position.

This invention relates to grinding machines and more particularly to apparatus for controlling a centerless grinding machine for throughfeed operation.

The centerless grinding machine is a frequently employed means for fashioning cylindrical precision-sized parts. Such a grinder conventionally has a rotating grinding wheel mounted on a machine bed; a regulating wheel mounted on a moveable slide; and a workrest blade mounted between the grinding wheel and regulating wheel. In operation workpieces or parts to be ground are placed on the workrest blade and the regulating wheel is moved on its slide toward the grinding wheel a sufficient distance to force the workpiece against the grinding wheel. The precise positioning of the regulating wheel is essential if the workpiece is to be ground to a precisely determined dimension. In the throughfeed grind ing operation to which this invention relates, workpieces are continuously fed onto the workrest and are ground in continuous succession between the grinding wheel and regulating wheel. The axes of the grinding and regulating wheels are slightly skewed to create a forward thrust on the workpieces during the grinding process. In some cases this thrust is the primary force which keeps the workpieces moving through the grinder. If the regulating wheel is retracted away from the workpieces the forward thrust ceases and the workpieces remain in position. In other cases gravity or power feed is used to move the workpieces along the workrest blade. In these cases a positive means is required to stop the flow of workpieces when desired.

Throughfeed grinding is to be distinguished from the so-called infeed grinding process where workpieces or portions of workpieces are individually ground one at a time with the regulating wheel being repositioned for the grinding of each workpiece. In throughfeed grinding the regulating wheel is initially positioned and this position is normally not changed as the workpieces move continually through the grinder.

As the series of workpieces is ground in this manner the grinding wheel gradually wears and its diameter decreases, causing the finished part dimension to increase.

One of the major problems in centerless throughfeed grinding is the correction of this grinding wheel wear, or wheel breakdown, as it is termed in the industry. In addition to wear, other factors such as heat may produce changes in final part size. This invention provides an improved means for correcting for Wheel breakdown and other causes of variation in final part size in centerless throughfeed grinding.

The present invention also provides apparatus for quickly disconnecting a power feed driving means from a grinding machine to permit a rapid and convenient changeover from a power drive to a manually controlled operation.

Centerless grinders are equipped with a handle or hand wheel by means of which an operator can move the regulating wheel on its slide toward or away from the grinding wheel. As wheel breakdown occurs and the finished part size is observed to approach a maximum tolerance value it is necessary to reposition the regulating Wheel relative to the grinding wheel. This is customarily done manually by turning the hand wheel slightly or by tapping the slide on which the regulating Wheel is mounted. This is often a troublesome procedure, especially when very small corrections have to be made reliably and quickly. Moreover, it has been found that the phenomenon of static friction prevents the reliable and controllable movement of the regulating wheel on its slide through very small distances such as 20 or 30 millionths of an inch which are frequently required for precision wheel breakdown correction.

Automatic power feeds have been attached to centerless throughfeed grinders to move the regulating wheel back and forth on its slide. These power feeds have been inconvenient for converting to manual infeed operation. By this invention it is quite easy to convert from through feed to infeed operation and vice versa.

The present invention provides an apparatus for overcoming the undesirable and unpredictable effects of static friction in correcting for grinding wheel breakdown in a. centerless throughfeed grinder equipped with a power feed. The apparatus for correcting for Wheel breakdown comprises the means for retracting the regulating wheel away from the series of workpieces, and a first grinding position, means for automatically advancing the regulating wheel back toward the workpieces and means for halting the regulating wheel at a second grinding position determined by an adjustable positioning means.

These and further objects and advantages of the present invention will be more readily understood when the following description is read in connection with the accompanying drawing in which:

FIGURE 1 is a perspective view of a centerless throughfeed grinder, and

FIGURE 2 is a schematic diagram of the electrical control system for the grinder.

The centerless throughfeed grinder of FIG. 1 comprises a machine bed 1 on which is mounted a grinding wheel 2. A regulating wheel 3 is mounted on a slide 4 and is capable of moving toward or away from the grinding wheel 2. Between wheels 2 and 3 is positioned a workrest blade 5 which supports a series of workpieces 6. The workpieces 6 are normally moved along the workrest blade by means of a gravity or power feed mechanism not shown. A solenoid operated clamp 7 is mounted over the workpieces and when energized it is capable of clamping a workpiece to the workrest blade and halting the flow of workpieces.

The regulating wheel 3 can be moved forward or backward on its slide by means of a lead screw 8 which can be turned by a handwheel 9. The grinder of FIG. 1 is also equipped with a power feed mechanism for turning this lead screw 8 to move the regulating wheel back and forth. The power feed comprises an air motor 10 capable of moving rod 11 in and out of the air motor cylinder. Coupled to rod 11 is an hydraulic check cylinder 12 capable of slowing or stopping the motion of rod 11. A cam 13 is rigidly attached to the lead screw 8 and the rod 11 is connected to the cam 13 by means of a cam follower 14. The connection of the power feed to the grinder seriously interferes with the manual use of the g'rind'e'r for precision infeed grinding operations. Although camfollower; 14 completely disconnects the cam" 13 from the restfo'f the power feeda'nd permits the manual rotatio'nf of the lead screw 8 without the drag'of the power reed; Installation machines has heretofore been objectionable because the drag associatedwith such power feeds has discouraged theuse of manual infeed operation for many jobs. The addition of'this quick disconnect advantageous in shops having limited facilities since it gfre l'y enlargesthe' range of applications for a grinding machine with power feed. The feature is also of great utility on the occasion of power feed failure.

' adjustable stop 15' is mounted on the machine bed 1? Stop 15 is a precision micrometer the positioning of which may be varied millionths of an inch by turning its; adjustment dial A switchbox 16 is mounted on the regulating wheel frame'17 so as to be in alignmenflwith the adjustable stop 15. The position of the regulating wheel is adjustably' controlled by the setting of the stop IS' in the manner to bedescribed:

Stop 15 and switchbox 16 are inFIG. 21. 'Switchbox 16 contains throw switc shown in more detail two' single pole-double es and 19, which are actuated by the moverneiitof actuating rod 20" having protrusions 21 and 22. R' 2tlfisiur'ge'd outwardly from the'box' by spring 23;

Wen thelregulating wheel: 3 is advanced toward the grinder wheel 2 switchbox 16 moves similarly" toward adjustable? stop 15; As wheel 3is' advanced there comes a point where" stop" 15 contacts actuating r'od 20 and further motion of wheel 3 pushes rod 20 against its spring 23', Protrns ions 21 and 22 are' positioned so that as the actuating rod 20is thus irnpelledswitch 18'is actu ated' before switch 19 is actuated; When switches 18 and 1' 'e'not actuatedby the protrusions 21 and'22 they are irrthe positions illustrated in FIG. 2;

The switching arm terminals of switches 18 and'19 are connected together and then through a pushbutton switch '24 to one sidew of retract coil25 associated with air motor When coil'25 is energized the air motor causes the regulating wheel to retract aw'ay fromthe grinding wheel. firstterminal of switch 18' is connected to advance coil-26, the energization of which moves the regulating wh l towa'rd the grinding wheel. A secondtermi'nal of switch 18 is connected to solenoid valve 27 associated he" hydraulic check 12. When solenoid valve 27 'gized it closes-one of the hydraulic circulation paths of 1 2'the'reby' loading and slowing the motion of rod 11. A first terminal of switch 19 is connected to the solenoid clamp 7 described above. A second terminal of switch 19 i s'connecte d to solenoid valve 28 which when energized closes a circulating path of the hydraulic check 12. When both valves 27 and28- are energized both circulating paths are closed and the fluid of the hydraulic chieck cannot circulate from one side of the hydraulic check. piston to the othenUnder such conditions the hydrauli'c check is locked in position and since it is connected to rod 11 locks the position of the lead screw 8 and thus regulating wheel 3. The arm terminals of s'w'che's 1'8 and 19,' are also connected to one side of an AC, power line 29. The other side of the power line is connected ot the solenoid clamp 7, coils 25 and 26, and vaivesm and 2s.

' In normal throughfeed grinding operation the regulating vwheel 3 'i's"advanced by means of the airmotor 10 toward "the grinder wheel2 u'ntil actuating rod 20 contacts adjustor heavy duty power feed on grinder feature is particularly able" stop 15:" As the" regulating-wheeb continues toadvance actuating rod 20 moves against its spring 23 and first switch 18 is actuated to the position opposite that shown in FIG. 2, energizing valve 27 and slowing the advance of the wheel 3. ,As"=the a'tlvance continues switch 19 is next actuated to clQSef-valve ZS v oi the regulating wheel 2'; The' positioriatwhichthe wheei 3 is halted depends uponthe position to which the micrometrically' adjustable stop 15 is; brought-:

Correction for wheel breakdownusing the present invention is made as follows. When the dimensions of the finished workpieces are observed to'approach an upper tolerance value due tothe efiect of wheel breakdown the o r i the correction process by making an appropriateadjustmentinthe setting of operator of the grinder initiates stop 15 and depressing" pu'shbutt bnswitch 24i This*"acti onF energizes retract coil 25 to move tlie' regulating wheel 3' away from the grindefwheel antl workpieces' the wheel 3 retracts; switc I move 'a'wa'y from stop 15. Under the urging ofsprin'g fli rod 20' moves outwardicausingswitclil to'ihe act ated to thepositionshown injFIG. 2, opening valve 28 energi'zing' solenoid clampfl" and=halting tlie movement of workpieces 6. If the workpieces are" moved" along the workrest blade 5 solely by the thrust caused by the slight skew between; the axes of the grinding and regulating wheelstlienthe workpieces will halt as" soon as herjegulating' wheel Sretra'cts' and the solenoid c'lairip 7' would be unnecessary. V 8 V I a Asfthej'rodlflcontinues it's outward movement switch 18' is neat actuated tolthe', osition shown in;FIG 2i opening valve 27 and energizing advancecbil' ZFfto'ca'tISe start ,ba'clg nward? the were cor by the normal action of stop 15' and the regulating wheel" 3'to re cted position switchtiex-lts'; V r T s Thismethod emanatin -tor wneetbre kaown wlir'e by the movement pr'weik ieces is halted; the reghl wheel is retracted away from the: series of workpie s and a first grindin'g' positi'on and" theii" automatically akf vancerl; back toward the 'wor f t a seed a grinding,position'determined by ti'ni adiu stop avoi all'tlie unpredictable elfe'ct's o f s tatie fr'ictiori in positiorling theregulatiiigwh l aild perfiiitsith" rection of tlirouglifeed gririding positionto with' 30 rnillionthsbf an inch; Precision. wheel brealidow re'ction' with' such" accuracy, c'dhvenie'n'ce reliability inipbs'sible in anonnaw grind n usingreview conventionalmaniialrnethods of adjirsthieiitl 7 It will be understood thhtvari ou's arrange; in tliefdetiails,

materials, steps and arrangement of parts which have beenherein d tainedand illustrated in; orde" to eiplain the nature of the invention may be made those skilled in thejar't within the principle and sco e of the'iiive'ntion as eipr'essed in the appeiided claims.

W r l m:

1'. Through feed conti'ol apparatus fora grinding-machihehaving aregulating wheel' means to a moving seriesofworkpieces and a grinding wheel into grinding contact, and driving means for moving said regulating wheel, comprising adjustable switch actuating means and switch meansjor producing signals to control saiddriving means, means for retractingthe regulating wheel away from the-series of workpiecesand grinding position, means for advancing" the regulating wheel automatically back toward the series of workpieces, meansfor' halting the regulating wheel at a second grinding position determined by the adjustment of 'the" switch actuating means,; and means for halting the rriovement of the series of workpieces while the regulating wheel is-retracted away from said workpieces. I I

2. Through eed control apparatus tor. a grinding machine having a regulatingwljeel movable to br g a naving seris'otwbrkpiecsand a g rii'idiugwhe el to grinding contact, and driving means for iiiovingsaidregulatifig and halt the advance boir 16" and acmatingfrod 29f Wheel, comprising adjustable switch actuating means and switch means for producing signals to control said driving means, means for retracting the regulating wheel away from the series of workpieces and a first grinding position, means responsive to the retraction of the regulating wheel for advancing the regulating Wheel automatically back toward the series of workpieces, means for halting the regulating wheel at a second grinding position determined by the adjustment of the switch actuating means, and means for halting the movement of the series of workpieces while the regulating wheel is retracted away from said workpieces.

References Cited UNITED STATES PATENTS Booth et a1 51165 X Harrison et al 51165 X Garberding 51103 Arlin 51-103 X Ohringer 51103 X LESTER M. SWINGLE, Primary Examiner. 

1. THROUGHFEED CONTROL APPARATUS FOR A GRINDING MACHINE HAVING A REGULATING WHEEL MOVABLE TO BRING A MOVING SERIES OF WORKPIECES AND A GRINDING WHEEL INTO GRINDING CONTACT, AND DRIVING MEANS FOR MOVING SAID REGULATING WHEEL, COMPRISING ADJUSTABLE SWITCH ACTUATING MEANS AND SWITCH MEANS FOR PRODUCING SIGNALS TO CONTROL SAID DRIVING MEANS, MEANS FOR RETRACTING THE REGULATING WHEEL AWAY FROM THE SERIES OF WORKPIECES AND A FIRST GRINDING POSITION, MEANS FOR ADVANCING THE REGULATING WHEEL AUTOMATICALLY BACK TOWARD THE SERIES OF WORKPIECES, MEANS FOR HALTING THE REGULATING WHEEL AT A SECOND GRINDING POSITION DETERMINED BY THE ADJUSTMENT OF THE SWITCH ACTUATING MEANS, AND MEANS FOR HALTING THE MOVEMENT OF THE SERIES OF WORKPIECES WHILE THE REGULATING WHEEL IS RETRACTED AWAY FROM SAID WORKPIECES. 